1. Field of the Invention
The present invention relates to an engine bearing, and in particular to a hydraulically damping engine bearing including fluid-filled chambers bordered at least partially by elastic walls, a limitedly deflectable diaphragm separating the chambers and at least one channel connecting the chambers.
2. Description of the Related Art
Engine bearings are known (e.g., German reference DE 34 46 725 C2) in which a separating wall is arranged between two chambers, where one chamber has an elastic diaphragm running in annular fashion on a rigid outer wall. An intermediate space formed by the elastic diaphragm and the rigid outer wall can be pressurized with an underpressure or vacuum to attain high rigidity of the engine bearing. If, during driving operation, the engine bearing is to be placed in the high rigidity state, it is necessary to apply the underpressure in the intermediate space so that the elastic wall thereby lies directly on the rigid outer wall of the bearing.
Further, engine bearings are known (e.g., German reference DE 42 38 752 C1) in which the chambers separated by a diaphragm are equipped with a flexible wall arranged in one of the chambers, for the purpose of changing the bearing characteristic. The bearing characteristic is changed by virtue of the fact that at low rigidity of the bearing, at least one of the hydraulic chambers works against a gas volume enclosed in the intermediate space, whereas at high rigidity, the flexible wall comes at least partially to rest on a stop. To aerate the intermediate space, a switch opens a flow connection to atmosphere or a pressure storage device, while to de-aerate, a valve is arranged in the flow connection. In a configuration of this type, the flexible wall is an integral part of a complete rubber bearing.
In addition, rubber bearings are known (e.g., German references DE 41 14 879 A1, DE 41 20 841 C1, DE 41 30 362 C2 and DE 41 03 028 C2) that are configured so that their rigidity is controllable. These rubber bearings are similar to conventional bearings, however, auxiliary energy in the form of pneumatic pressure or hydraulic pressure is required. FIG. 4 in German reference DE 41 30 362 C2 shows a bearing equipped with a mechanical adjustment device.
Also known (e.g., PCT reference WO 96/17184), is a hydraulically damping engine bearing with a conventional suspension spring connected in series. However, the conventional suspension spring is taken out of operation in the high rigidity position. Disadvantageously, an expensive switching module is required. Moreover, auxiliary energy in the form of pressure is also required.